Research supported by Grant NS 1447-17 has disclosed a pronounced latent facilitatory effect of glucocorticoids on mammalian motor nerve. This was uncovered by earlier developed methodology that enables motor nerve function to be monitored in the cat in vivo. Because of the important therapeutic and physiologic implications of this glucocorticoid effect, next year's research will expand these studies. Initial experiments will query whether this corticosteroid effect is selective for motor nerve terminal transmitter function or is a manifestation of more general changes in the neuron. Alterations in the electrophysiologic properties of the neuron and effects on transmitter dynamics will be determined. Effects on axoplasmic transport will be studied. Effects on the cellular structure and ultrastructure of motor neuron will be examined. Eventually the biochemical alterations related to other observed glucocorticoid effects will be sought. Meanwhile the parameters of glucocorticoid effects on motor nerve as already defined in relation to therapeutic applications (see Progress Report, May, 1974) will be re-examined to determine the influence of this hormonal action on degenerative processes in the neuron. The technique of subacute denervation as developed through this grant (NS 1447) support Will be invaluable for this.